A charged particle beam device such as a scanning electron microscope (SEM) that acquires a high-magnification image scans a sample with a focused electron beam, and detects secondary electrons emitted from the sample.
The detected secondary electrons are supplied as a video signal to a display synchronized with two-dimensional scanning using an electron beam. In a case where the charged particle beam device of the related art is used, since a state of a surface structure of the sample is able to be observed with high magnification, the charged particle beam device is used in a wide industrial field.
In a case where an image is observed by the charged particle beam device, a user initially transmits a command for operating a device main body to the device main body from a terminal such as a personal computer. The device main body of the charged particle beam device receives the command from the terminal. According to the content of the received command, the device main body detects an image (enlarged image) of the sample while moving the stage having the sample mounted thereon, changing a posture of the stage, or switching the scan modes in which the charged particle beam is irradiated from the electron beam source.
The device main body converts the enlarged image of the sample into image data such as a video signal, and transfers the image data to a terminal of the user from the device main body through a communication network line. The user displays the image on a terminal screen, and observes the displayed image.
A so-called Ethernet (registered trademark) line is used as the communication network line that connects the device main body and the terminal of the user. The Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) have been known as the communication protocol using Ethernet (registered trademark).
TCP is a transfer mode that prioritizes reliability rather than a communication speed. For example, even in a case where any failure occurs and packets are missing, a mechanism for increasing reliability is provided in TCP like a case where the missing packets are transferred again. In TCP, communication reliability is high, but a communication speed is relatively low since the overhead of a protocol process is large.
UDP is a transfer mode that prioritizes a communication speed rather than the communication reliability. For example, in a case where the packets are missing, the missing packets are not transferred again in UDP. Accordingly, since a protocol process is simple and the overhead thereof is small, it is possible to perform high-speed communication in UDP.
In PTL 1, the transfer modes are switched in the electron microscope in which a capacity of a communication network line is changed. Accordingly, it is possible to increase an update rate of the image in PTL 1 both in a case where the line capacity is large and in a case where the line capacity is small.